This shows an example of the class of 20 electric locomotives introduced by the Metropolitan Railway from 1922 onwards. Although they looked like new units, they were in fact drastic rebuilds of earlier stock, with much more powerful motors. They were used for many years before 1961 to haul Metropolitan trains from the City and Baker Street to (originally) Verney Junction and (later) Aylesbury, the electric loco being used as far as Rickmansworth where a steam locomotive would take over.